A stacking panel shutter door consists of multiple door panels spanning the entire door width that are stacked one on top of the other when the shutter is in the closed position. When such a door shutter is actuated to open, the panels contained within opposed guide members are lifted upwards, detach from each other and upon reaching the top of the guide members that they are travelling on, they change direction and are then collected in a stacked face-to-face relationship in a console. An example of such a stacking panel shutter door is described in Singapore patent application number SG10201403775Y and inter alia, shows an operating mechanism comprising an arrangement of sprockets linked by lifting chains and powered by a motor.
As any particular set of the door panels are likely to be relatively large in size and constructed of a variety of materials (which may include glass), they can be quite heavy which will require a motor with a particularly large lifting capacity to lift each of the panels. Such a motor has to be large in size and in reality this may not be practical or even available.
Accordingly, to assist in lifting the load and thus reduce the need for a large motor, a common solution is to incorporate a counter-balancing system. Counter-balancing systems for stacking panel shutter doors that are widely-used are those that employ torsion springs such as the one described in PCT/SG2015/000132. However, the construction of the springs themselves needs to be sized according to the width and height of the door shutter as well as the weight of the door panels.
When these parameters get larger, there will be constraints in the design of the torsion springs. For example, if the height of the door shutter is particularly high, the springs will need to make more turns to accommodate the longer travel of the door panel and thus the or each spring employed will need to be longer in length. However, since the space available to accommodate the or each spring length will be limited by the width of the door, there may be insufficient space to accommodate the or each spring needed as a counter balance against the door panel weight.
Accordingly, in order to keep the same sized motor, it is an object of the present invention to try and alleviate the aforementioned problem through the provision of an improved counter-balancing system for a stacking panel shutter door that employs one or more torsion springs.